1-amidino-3-(substituted-phenyl) urea antimalarial composition and method of use

ABSTRACT

Compositions for use as antimalarials which comprise a 1amidino-3-(substituted-phenyl)urea compound of the formula   OR A PHARMACEUTICALLY ACCEPTABLE ACID ADDITION SALT THEREOF WHEREIN Y4 is halogen, trifluoromethyl, cyano or nitro, and the Y&#39;&#39;s are selected from halogen, trifluoromethyl, cyano, nitro, methyl and hydrogen, provided that at least one of the Y&#39;&#39;s is a substituent other than hydrogen except where Y4 is cyano or trifluoromethyl, and provided that Y4 and any one of the Y&#39;&#39;s are not the same substituent when any one of them is selected from cyano, nitro, trifluoromethyl and methyl, and further provided that not more than two of the Y&#39;&#39;s is a substituent other than hydrogen, and a pharmaceuticaly acceptable carrier. And a method for treatment or prophylaxis of malaria in mammals which comprises administering an effective anti-malarial amount of a 1-amidino-3-(substituted-phenyl)urea compound as herein defined or a pharmaceutically acceptable acid addition salt thereof.

[451 Sept. 25, 1973 1 1 1-AMlDlNO-3-(SUBSTITUTED-PHENYL) UREA ANTIMALARIAL COMPOSITION AND METHOD OF USE [76] lnventor:

Leslie Percy Walls, 183-193 Euston Rd., London, England [22] Filed: June 30, 1970 211 App1.No.: 51,322

Related US. Application Data [63] Continuation-impart of Ser. No. 650,225, June 30,

1967. Pat. No. 3,539,616.

[52] US. Cl. 424/304, 424/322 [51] Int. Cl A61k 27/00 [58] Field of Search 424/304 [56] References Cited UNITED STATES PATENTS 3.539.616 11/1970 Walls 424/304 FORElGN PATENTS OR APPLICATIONS 1.194.835 I 6/1970 Great Britain 424/304 1.548.340 lO/1968 France 424/304 OTHER PUBLICATIONS Tetrahedron, 1960, Vol. 10. pp. 12-25 I Nature, 1960. April 9,'Vol. 186. pp. 170-171 Chemical Abstracts Subject lndex-Sixth Collective lndex Sp-Z pp. l2l35S-l2l36S (1966) Primary Examiner-Albert T'. Meyers Assistant Examiner-Norman A. Drezin Attorney-Dike, Thompson and Bronstein, Sewall P. Bronstein andDon ald Brown [5 7 ABSTRACT Compositions for use as antimalarials which comprise a 1-amidino-3-(substituted-phenyl)urea compound of the formula or a pharmaceutically acceptable acid addition salt thereof wherein Y is halogen, trifluoromethyl, cyano or nitro, and the Ys are selected from halogen, trifluoromethyl, cyano, nitro, methyl and hydrogen, provided that at least one of the Ys is a substituent other than hydrogen except where Y is cyano or trifluoromethyl, and provided that Y and any one of the Ys are not the same substituent when any one of them is selected from cyano. nitro, trifluoromethyl and methyl, and further provided that not more than two of the Ys is a substituent other than hydrogen.and a pharmaceuticaly acceptable carrier.

And a method for treatment or prophylaxis of malaria in mammals which comprises administering an effective anti-malarial amount of a l-amidino-3-(substituted-phenyl)urea compound as herein defined or a pharmaceutically acceptable acid addition salt thereof.

14 Claims, No Drawings l-AMIDINO-3-(SUBSTITUTED-PHENYL) UREA ANTIMALARIAL COMPOSITION AND METHOD OF USE This application is a continuation-in-part of U.S. Pat. application Ser. No. 650,225 filed June 30, 1967, now U.S. Pat. No. 3,539,616.

This invention relates to l-amidino-3-(substitutedphenyl)urea compounds and more particularly to selected compounds of the above general class of compounds, which are highly and unexpectedly effective as antimalarial drugs.

During the last 40 years, a number of safe and highly effective synthetic chemicals have been developed for use against malaria infections in humans. These chemicals include chloroquine, proguanil (chloroguanide),

primaquine and pyrimethamine. All are currently used for treating various forms of infection, but no single synthetic antimalarial drug is ideal for treatment and prophylaxis of all malaria infections. Resistance to these drugs by malaria parasites has now been reported from various parts of the world and this has stimulated research into new types of antimalarial drugs to add to the armory of the physician.

l(N-Alkylamidino)-3-phenylureas are a class of synthetic chemicals which were investigated in the late I940s for antimalarial activity and were found not worthy of further investigation. (Curd, F.H.S. et al., J. Chem.Soc., 1949, 1732). Further, l-amidino-3- phenylureas were investigated by Urbanski in 1960, who indicated that, of a large class of l-amidino-3- (monosubstituted-phenyl)ureas, the highest activity against the malaria parasite Plasmodium gallinaceum in chicks was obtained with l-amidino-3-(4- nitrophenyl)urea. (Skowronska-Serafin, B. & Urbanski, T., Tetrahedron, 10, 12-25 (1960)).

It has now been found that compounds of formula (I) also have activity as antimalarials.

NII

Y is trifluoromethyl or nitrile when Y is hydrogen or is a substituent halogen or methyl at the 2- or 3- position; or

Y is nitro when Y is a substituent trifluoromethyl or halogen at the 3- position.

It has now been further found that compounds embraced by the statement of formula (la) also possess marked anti-malarial activity, and some are superior to the compounds embraced in the narrower statement of formula (I) I NII In formula (Ia), Y and Y are halogen and Y is selected from the class consisting of halogen and cyano. In formulae (I) and (la), halogen is chlorine, bromine,

fluorine and iodine, but chlorine is especially preferred. Compounds embraced by formula (Ia) include: l-Amidino-3-( 3,5-dichlor0-4-cyanophenyl)urea l-Amidino-3-(3,4,5-tribromophenyl)urea l-Amidino-3-(3,4-dibromo-4-chlorophenyl)urea 1-Amidino-3-(4-bromo-3,5-dichlorophenyl)urea 1-Amidino-3-(3,4,5-trichlorophenyl)urea and their'acid addition salts.

The following preferred compounds of formula (I) and their acid addition salts exhibit exceptional activity as antimalarials: l-Amidino-3-(4-chloro-3-cyanophenyl )urea l-Amidino-3-(3-chloro-4-cyanophenyl)urea l-Amidino-3-(3,4-dichlorophenyl)urea l-Amidino-3-( 4-trifluoromethylphenyl )urea l-Amidino-3-(4-chloro-3-trifluoromethylphenyl)urea.

It has also been found that the following compounds of formula (I) and their acid addition salts, exhibit a high activity as antimalarials: l-Amidino-3-(4-cyanophenyl)urea l-Amidino-3-(4-cyano-3-methylphenyl)urea l-Amidino-3-( 3-chloro-4-nitrophenyl )urea l-Amidino-3-(4-cyano-3-fluorophenyl)urea l-Amidino-3-(4-cyano-2-methylphenyl)urea The following compounds of formula (I) and their acid addition salts have been found to exhibit marked activity as antimalarials: l-Amidino-3-(2-chloro-4-cyanophenyl)urea l-Amidino-3-(4-chloro-3-nitrophenyl)urea.

Activity as ,antimalarials is also exhibited by the following compounds of formula (I) and their acid addition salts. l-Amidino-3-(2-bromo-4-cyanophenyl)urea l-Amidino-3-(4-nitro-3-trifluoromethylphenyl)urea l-Amidino-3-(2,4,54richlorophenyl)urea.

Amidinourea compounds of the present invention exhibiting antimalarial activity are therefore embraced by the following formula (Ib) (III) In fonnula (lb) Y is halogen, trifluoromethyl, cyano or nitro, and the Y's are selected from halogen, trifluoromethyl, cyano, nitro, methyl and hydrogen, provided that at least one of the Y's is a substituent other than hydrogen except where Y is cyano or trifluoromethyl, and provided that Y and any one of the Y's are not the same substituent when any one of them is selected from cyano, nitro, trifluoromethyl and methyl, and further provided that not more than two of the Y's is a substituent other than hydrogen.

The amidinoureas of formulae (I), (la) and (lb) and their acid addition salts, are active against P.gallinaceum in chicks and P. vinckei and P. berghei in mice. They are also active against strains of P. gallinaceum resistant to pyrimethamine or dihydrotriazines and strains of P. berghei resistant to chloroquine. The compounds of formula (I) are also more active against P. gallinaceum and, in many instances, are also more active against P. vinckei than the known 1- amidino-3-(4-nitrophenyl)urea.

The activities of the above-listed compounds reside in the base and the acid in the acid addition salts is of (in which X is an imino group) may be converted to a compound of formula (lb) by reaction with excess of nitrous acid, preferably at to or by hydrolysis with a strong aqueous acid, for example ethanesulphonic acid, methanesulphonic acidorhydrochloric acid, preferably between about 20 to 90C. The biguanide starting materials may be made by a number of methods well documented in the literature (see for example Chemistry of Carbon Compounds Ed. EH. Rodd, 1st edn. Vol. III Part A, 1954 at p. 198 et seq.).

As another example, a S-alkyl-l-amidino-3- (substituted-phenyl)-thiourea of formula (II) (in which X is an S-alkyl group) may be oxidised to a compound of formula (lb), preferably using a peroxide, for example hydrogen peroxide, as an oxidising agent. The S-substituted-thiourea starting material may be prepared from the corresponding l-amidino-3-(substituted-phenyl) thiourea, which itself may be made by reaction of the appropriate isothiocyanate with guanidine.

Another type of method of preparing amidinoureas of formula (lb) is by the reaction of guanidine with a reactive derivative of a substituted-phenylcarbamic acid of formula (III) (III) for example an isocyanate (the internal anhydride), or an urea (the amide). Other reactive derivatives which may be used are esters, for example, a urethane which is preferably reacted with an anhydrous solution of guanidine base. A substituted-amide may also be used, for

example, fusion of an N,N-dialkyl-N'-arylcarbamide dium hydroxide yields the 1-amidino-3-(substitutedphenyl)urea base.

For treatment or prophylaxis of malaria, the compounds of formulae (I), (la) or (lb) may be presented with an acceptable carrier therefor as pharmaceutical compositions, preferably as a tablet for oral administration. The compositions may be made by any convenient method comprising the admixture of the components. The substituted-amidinourea may be in the form of its base or as an addition salt thereof.

For oral administration, fine powders or granules of the compounds may contain diluents and dispersing and surface active agents and may be presented in a draft, in water, or in a syrup; in capsules or cachets in the dry state, or in an aqueous or non-aqueous suspension, when a suspending agent may also be included; in tablets, preferably made from granules of the active ingredient with a diluent by compression with binders and lubricants, or in a suspension in water or a syrup, or an oil, or in a water/oil emulsion, when flavouring, preserving, suspending, thickening and emulsifying agents may also be included. The granules or the tablets may be coated, and the tablets may be scored.

For parenteral administration, the compounds may be presented in unit dose or multi-dose' containers, in aqueous or non-aqueous injection solutions which may contain antioxidants, buffers, bacteriostats and solutes which render the compounds isotonic with the blood, or in aqueous or non-aqueous suspension when suspending agents and thickening agents may also be included, extemporaneous injection solutions and suspensions may be made from sterile powders, granules or tablets which may contain diluents, dispersing and surface active agents, binders and lubricants.

In treating infections of malaria in animals and mammals (i.e., man), a dose of from 1 to l00 mg/kg. of body weight of a compound of formula (lb) or a salt thereof estimated as the base would be used, and preferably a dose from 5 to 25 mg./kg. of body weight. For administration of the amidinourea compounds of this invention in unit dose composition for example tablets or cachets, each unit may contain from 50 mg. to 7000 mg. of a compound of the invention, and preferably from mg. to 500 mg., estimated as the base.

The present invention provides a process for the treatment or prophylaxis of malaria, which comprises administering a compound of formula (I), (la) or (lb), preferably in an amount within the dose range from 1 to 100 mg./kg., to the host or potential host (i.e., mammal, warm-blooded animal such as man, mice and chickens) of the infection. The present invention also provides a composition for use as an antimalarial which comprises a compound of the formula (I), (la) or (lb) or a pharmaceutically acceptable acid addition salt thereof as herein before defined, in association with a pharmaceutically acceptable carrier therefor.

The following are Examples of this invention. (All temperatures are in degrees Celsius).

EXAMPLE 1 4-Chloro-3-cyanoaniline (6.1 g.), dicyandiarnide (3.7 g.), water (16 ml.) and concentrated hydrochloric acid (3.6 ml.) were heated under reflux for 30 minutes. With cooling a hydrochloride crystallised which was collected by filtration and washed with a little water. This crude salt was dried and recrystallised from alcohol. 4-Chloro-3-cyanophenylbiguanide hydrochloride then separated as white needles (6.4 g.), m.p. 233 with effervescence. The basewas obtained as small white needles when the solution of this salt was made alkaline with sodium hydroxide; recrystallised from alcohol, it formed colourless prisms, m.p. 202 with effervescence.

The biguanide base (3.2 g.) was dissolved in N- ethanesulphonic acid (32 ml.) and kept at 90 for 2 hours, during which period colourless crystals of 1- amidino-3-(4-chloro-3-cyanophenyl)urea ethanesulphonate separated. This salt was collected after cooling (2.8 g.), and was recrystallised from methanol (or water) and formed white needles, m.p. 219. The base was obtained by treating an aqueous solution of the salt with sodium hydroxide. lt formed white needles, m.p. 222, which could be further purified by recrystallisation from alcohol. This substance was sparingly soluble in water.

EXAMPLE 2 In the manner described in Example 1, 3-chloro-4- cyanoaniline was converted to 3-chloro-4- cyanophenylbiguanide hydrochloride, which formed white matted needles from methanol, m.p. 258 with effervescence (the corresponding base formed white prisms from alcohol, m.p. 181).

The biguanide (5 g.) was dissolved in 0.5N- ethanesulphonic acid (100 ml.) and the solution was kept at 90 for 2 hours. With cooling, a high yield of lamidino-3-(3-chloroP4-cyanophenyl)urea ethanesulphonate crystallised in white prisms, m.p. 224 (the corresponding base crystallised from alcohol had a m.p. 213).

EXAMPLE 3 Dichloramine-T (6 g.) was added to a solution of 4- cyanoaniline (5.9 g.) in chloroform (59 ml.). After 4 hours the filtered solution was evaporated and the residue was lixiviated with N-NaOH. The undissolved crystalline material (6 g.) was 2-chloro-4-cyanoaniline, m.p. 99-l00; after recrystallisation from aqueous alcohol it had a m.p. 102.

2-Chloro-4-cyanoaniline (4.2 g.), dicyandiamide (7.5 g.), concentrated hydrochloric acid (6.6 ml.) and water (15 ml.) were heated under reflux for 15 minutes. The crude hydrochloride that crystallised with cooling was separated, dried and heated with alcohol. The residue (4.1 g.) of 2-chloro-4- cyanophenylbiguanide hydrochloride had a m.p. 243 with effervescence, and a m.p. of 244 after recrystallisation from water (the corresponding base formed white needles, m.p. 193 with effervescence).

When a solution of the biguanide (3.5 g.) in N- ethanesulphonic acid (35 ml.) was kept at 90 for 3 hours and then cooled, l-amidino-3-(2-chloro-4- cyanophenyl)urea ethanesulphonate (4.4 g.) separated in colourless prisms, m.p. 21 l2l4; recrystallisation from methanol gave a product, m.p. 214 (the corresponding base formed white needles, m.p. 210 with effervescence).

EXAMPLE 4 2-Bromo-4-cyanoaniline was converted in the manner described in Example 3 to 2-bromo-4- cyanophenylbiguanide hydrochloride, m.p. 234 (the corresponding base, white needles, m.p. 200). This biguanide was converted in the manner described in Example 3 to l-amidino-3-(2-bromo-4-cyanophenyl)urea ethanesulphonate, white prisms from methanol, m.p.

5 210 (corresponding base formed white needles, m.p.

206 with effervescence).

EXAMPLE 5 4-Cyano-3-methylaniline was converted in the man- 10 ner described in Example 1 to 4-cyano-3- methylbiguanide hydrochloride, m.p. 232 after recrystallisation from water (the corresponding base had m.p. 172 after recrystallisation from alcohol). In the manner described in Example 1, this biguanide was converted into 1-amidino-3-(4-cyano-3- methylphenyl)urea ethanesulphonate, white prisms from water, m.p. 232 (the corresponding base formed white leaflets after crystallisation from water, m.p.

EXAMPLE 6 4-Cyano-2-methylaniline was converted in the manner described in Example 1 to 4-cyano-2- EXAMPLE 7 To a solution of 4-cyanoaniline (5.9 g.) in acetone (60 ml.) were added anhydrous sodium carbonate (5.3 g.) and ethyl chloroformate (5.5 g.). The mixture was heated under reflux for 3 hours and then filtered. The filtrate was evaporated to dryness and the residue was crystallised from aqueous alcohol. The product, pcyanophenylurethane, formed pale yellow prisms (7.4 g.), m.p. ll5.5.

Guanidine hydrochloride (2.9 g.) was added to a solution of sodium (0.7 g.) in ethanol (60 ml.). p- Cyanophenylurethane (4.9 g.) was then added and the mixture was heated under reflux for 4 hours and filtered hot. The residue left after evaporation of the filtrate'was lixiviated with aqueous alcohol (20 ml. alcohol, 10 ml. water). The undissolved crystalline residue of crude l-amidino-3 -p-cyanophenylurea (1.5 g.), m.p. ca. 199, was purified by recrystallisation from N- ethanesulphonic acid as the ethanesulphonate, m.p. 219220, identical with the product described in Example 9.

EXAMPLES 1n the manner described in Example 1, 3,4- dichloroaniline was converted to 3,4-

dichlorophenylbiguanide hydrochloride, which formed white needles, m.p. 230, from water (the corresponding base: white leaflets after separation from alcohol, m.p. 154). This biguanide was converted in the manner of Example 1 to 1-amidino-3-(3,4- dichlorophenyl)urea ethanesulphonate, which gave white prisms from water, m.p. 224 (the corresponding base: hydrated white needles after separation from water, m.p. 95-98).

EXAMPLE 9 p-Cyanoaniline (1 1.8 g.) was dissolved in 2N- hydrochloric acid (50 ml.) at 90 and the solution was stirred as dicyandiamide (8.4 g.) was added. The mixture was heated under reflux for 30 minutes, the product, p-cyanophenylbiguanide hydrochloride, separating meanwhile. After cooling, this salt (20 g.) was collected and washed with water, m.p. 277 with decomposition.

Metathesis of this salt with silver ethanesulphonate in water furnished a solution of p-cyanophenylbiguanide ethanesulphonate, evaporation of which gave the crystalline salt. Recrystallisation from alcohol gave white leaflets, m.p. 209-'21 1.

A solution of p-cyanophenylbiguanide ethanesulphonate 13.5 g.) in ethanesulphonic acid (120 ml.) at room temperature slowly deposited colourless prisms of l-amidino-3-(4-cyanophenyl)urea ethanesulphonate, m.p. 2l8-2l9 with effervescence. A yield of 50 percent was obtained in 7 days but longer standing gave 80 percent A solution of the urea ethanesulphonate salt in hot water was made alkaline with ION-sodium hydroxide and the base crystallised in white prismatic needles, m.p. 205 with effervescence.

A solution of p-cyanophenylbiguanide ethanesulphonate (10 g.) in ethanesulphonic acid (500 ml.) was treated-dropwise with a concentrated aqueous solution of sodium nitrite ('20 g.). The flocculent precipitate that first formed redissolved, and effervescence followed by precipitation ensued. After 2 hours the solid was collected and washed with cold water. It was dis solved in hot water and ION-sodium hydroxide was added. 1-Amidino-3-(4-cyanophenyl)urea separated as rather discoloured prismatic needles, m.p. 205 with effervescence.

EXAMPLES 10 AND 11 Tablets of l-amidino-3-( 2-chloro-4- cyanophenyDurea ethanesulphonate were prepared from the following ingredients:

' Example 10 Example 11 Amidinourea ethanesulphonate 100mg. 200 mg. Lactose B.P. 125 mg. 100 mg. Starch 5.1. 60 mg. 75 mg. Magnesium steal-ate B.P. mg. mg.

The tablets of Example 10 were prepared by moist granulation and compression using a 10 percent gelatin solution as a granulating agent; and those of Example 11 using an alcoholic solution of polyvinylpyrrolidine.

EXAMPLE l2 p-Aminobenzotrifluoride hydrochloride (7.92 g.), dicyandiamide (10.08 g.), concentrated hydrochloric acid (7.04 ml.) and water (20 ml.) were heated under reflux for 15 minutes and the resulting solution was cooled and made alkaline. The base separated as an oil which slowly solidified and was extracted with ether. The extract was dried with anhydrous sodium sulphate and evaporated, and the residue was heated at 90 in solution in N-ethanesulphonic acid (100 ml.). After 2 hours the reaction mixture was cooled and the crystalline product was collected (6.5 g.). Recrystallisation from methanol afforded l-amidino-3 -ptrifluoromethylphenylurea ethanesulphonate, m.p.

222", as white prisms (the base crystallised from water in white leaflets, m.p. 173).

EXAMPLE l3 4-Chloro-3-nitroaniline (6.8 g.), dicyandiamide (5.04 g.) and 4N-l-lCl (15 ml.) were heated under reflux for 15 minutes and the reaction mixture was filtered while hot from a small residue. The filtrate was made alkaline, and the crude basic material that separated was collected and lixiviated with cold 0.2N-acetic acid (total of 300 ml.). The undissolved residue (2.3 g.) was crystallised from alcohol and gave buff prisms of the sparingly-soluble acetate of l-amidino-3-(4-chloro- 3-nitrophenyl)urea, m.p. l75.5 with effervescence. The acetic acid extract was made alkaline and the precipitated base was crystallised from aqueous alcohol, affording brown prisms (6.5 g.) of 1-(4-chloro-3- nitro)phenylbiguanide, m.p. 164. This biguanide was converted in the manner described in Example 1 into 1-amidin0-3-(4-chloro-3-nitrophenyl)urea ethanesulphonate which crystallisedfrom methanol in pale yellow prisms, m.p. 2l4-2 15. The base crystallised from alcohol in yellowneedles, m.p. 213 with effervescence.

EXAMPLE l4 2-Chloro-5-nitrobenzotrifluoride (J. Org. Chem., 1957, 22, 300) (22.5 g.) was added dropwise with stirring to a solution of .stannous chloride dihydrate (67.8 g.) in ethanol (325 ml.) and concentrated hydrochloric acid (60 ml.). After the addition, the solution was heated on the steam-bath for 30'minutes. Alcohol was distilled off and the residue was poured into excess of ION-NaOl-l. The basic oil thus liberated was collected in ether, dried with anhydrous sodium sulphate, and distilled. 4-Chloro-3-trifluoromethylaniline was obtained, m.p. l18120/17 mm. Hg.; refractive index u 1.5150. The product crystallised and had m.p. 38-39.

This aniline (5.9 g.), dicyandiamide (5.5 g.) and 4N- l-lCl (15 ml.) were heated under reflux for 15 minutes. With cooling a crystalline hydrochloride separated (6 g.) which, on recrystallisation from water, gave white leaflets of 4-chloro-3-trifluoromethylphenylbiguanide hydrochloride, m.p. 210-211. A solution of the base of this biguanide (3.5 g.) in normal methane-sulphonic acid was heated to and after 25 minutes crystals began to separate. After 2.5 hours the reaction mixture was cooled, and the crude product collected and recrystallised from methanol. l-Amidino-3-(4-chloro-3- trifluoromethyl)phenylurea methanesulphonate crystallised as white needles, m.p. 239-240 with decomposition.

EXAMPLE 1s 3-Chloro-4-cyanoaniline (15.2 g.), dicyandiamide (16.8 g.) and 4N-hydrochloric acid (50 ml.) were heated under reflux until solid began to separate. The reaction mixture was then kept at for 30 minutes, cooled and filtered. The solid was dried, and heated with alcohol (200 ml.). After cooling, the residual solid (23 g.) was collected, washed with alcohol and dried. This substance, 3-chloro-4-cyanophenylbiguanide hydrochloride, m.p. 257-25 8, with decomposition, was dissolved in boiling water (300 ml.) and the solution was made alkaline with ION-sodium hydroxide. After cooling, the biguanide base was collected and washed with water, m.p. l74-l75 with effervescence, pure enough for the next step.

' The base (16.4 g.) was dissolved in N- ethanesulphonic acid (164 ml.) and the solution was kept at 100 for 2 hours and then cooled. The crystalline l-amidino-3 -(3-chloro-4-cyanophenyl)urea ethanesulphonate thus obtained had m.p. 223-224 with effervescence. Recrystallisation from water or methanol gave colourless prisms of similar meltingdecomposition properties. This salt was dissolved in hot water and the solution was made alkaline (ION-sodium hydroxide). The base separated in white leaflets, m.p. 212213 with effervescence, little changed by recrystallisation from alcohol.

EXAMPLE l6 3-Chloro-4-cyanoaniline (1.52 g.), dicyandiamide (0.84 g.) and N-ethanesulphonic acid (20 ml.) were heated at 100 for 2 hours. After cooling, the solid product was collected by filtration, dried, and then heated with alcohol. After cooling, the undissolved solid was collected and washed with alcohol. The crystalline residue, m.p. 223 with decomposition, was identical with the ethanesulphonate of Example 2.

When N-ethanesulphonic acid was replaced by N- methanesulphonic acid, the corresponding methanesulphonate, m.p. 249-250 with decomposition, was produced.

EXAMPLE 17 3-Chloro-4-cyanoaniline (1.52 g.), dicyandiamide (1.68 g.) and N-hydrochloric acid (30 ml.) were heated under reflux for 15 minutes. Some decolourising charcoal was added, followed by filtration at the boiling point. The filtrate deposited white needles of lamidino-3-(3-chloro-4-cyanophenyl)urea hydrochloride, which decomposed about 250.

The same product was obtained when 3-chloro-4- cyanophenylbiguanide was heated for a short period under reflux with dilute hydrochloric acid.

EXAMPLE l8 1-Amidino-3-(3-chloro-4-cyanophenyl)urea ethanesulphonate (1.74 g.) was dissolved in boiling methanol 150 ml.) and the solution was treated with a solution of dry sodium embonate (1.08 g.) in methanol (50 ml.) and water (50 ml.). The solution was heated under reflux and in a few moments l-amidino-3-(3-chloro-4- cyanophenyl)urea embonate crystallised. It was collected by filtration and washed with water, m.p. 195 with effervescence.

EXAMPLE 19 The urethane, methyl 3-chloro-4-cyanophenyl carbamate, m.p. 136, was prepared from 3-chloro-4- cyanoaniline by the method of Example 7. This substance (4.5 g.) was heated under reflux for 4 hourswith a solution of guanidine (from 2.5 g. of the hydrochloride) in ethanol. With cooling, crystalline solid (0.5 g.) separated, evaporation giving a second crop (0.9 g.). This crude base was purified by dissolving it in the calculated amount of hot aqueous ethanesulphonic acid. With cooling there separated l-amidino-3-(3-chloro-4- cyanophenyl)urea ethanesulphonate, m.p. 223-224 with decomposition, from which the base, m.p. 21 l.5

with decomposition, was obtained. These products were identical with those of Example 15.

EXAMPLE 20 EXAMPLE 21 4-Nitro-3-trifluoromethylaniline (6.18 g.), dicyandiamide (7.54 g.) and 4N-hydrochloric acid (22.5 ml.) were heated under reflux for 10 minutes to provide a clear solution. The solution was made alkaline (ION- sodium hydroxide) and the'precipitate that formed was collected and washed with water. The crude base was extracted with hot 2N-acetic acid (50 ml.) and the extract was made alkaline (ION-sodium hydroxide), thus precipitating 4-nitro-3-trifluoromethylbiguanide, which gave orange prisms from alcohol, m.p. 149-150.

Reaction of this biguanide (4.8 g.) with normal methanesulphonic acid by the method of Example 14 gave l-amidino-3-(4-nitro-3-triflu0romethylphenyl)urea methanesulphonate in yellow needles, m.p. 245 with decomposition; the base, on crystallisation from aqueous alcohol, formed pale yellow silky needles, m.p. 202 with effervescence.

EXAMPLE 22 The procedure of Example 15 was applied to 4- cyano-3-fluoroaniline (U.S. application Ser. No. 522,817). The biguanide hydrochloride separated from the reaction mixture and had m.p. 274 with decomposition the base formed white plates, m.p. 169.5 with effervescence.

l-Amidino-3-(4-cyano-3-fluorophenyl)urea methanesulphonate crystallised from waterin white prisms, m.p. 241-242 with effervescence; the base had m.p. 205-206 with effervescence.

EXAMPLE 23 The procedure of Example 21 was applied to 3- chloro-4-nitroaniline. The biguanide crystallised from alcohol in yellow leaflets, m.p. 178, and 1-amidino-3- (3-chloro-4-nitrophenyl)urea methanesulphonate from water in yellow prisms, m.p. 241 with decomposition.

EXAMPLE 24 3, 4, S-Trichloroaniline (4.9 g.), dicyandiamide (4.2 g.) and 4N-hydrochloric acid (12.5 ml.) were heated under reflux. In a few minutes a clear solution was obtained, followed by separation of the product. After cooling the product, 1-(3,4,5-trichlorophenyl) biguanide hydrochloride, was collected, recrystallisation of which from water gave white needles (7.15 g.), m.p. 264 with decomposition. A solution of this salt in water was made alkaline and the base was precipitated as white leaflets of the monohydrate, m.p. 184 with vigorous effervescence.

A solution of the aforementioned biguanide (4.5 g.) in ethanesulphonic acid (45 ml. of normal aqueous solution) was heated at 90 for 2 hours. l-Amidino-3- (3,4,5-trichlorophenyl) urea ethanesulphonate separated, and after cooling was collected and washed with water. This salt had m.p. 245246, not elevated by recrystallisation from methanol.

The aqueous solution of the salt was made alkaline and the base separated as a crystalline solid which was recrystallised from aqueous alcohol, forming white prismatic needles of the base hydrate, m.p. 193.

EXAMPLE 25 4-Bromo-3,S-dichloroaniline (2.41 g.), dicyandiamide (2.52 g.), 4N-hydrochloric acid (7.5 ml.) and ethanol (7.5 ml.) were heated under reflux. The hydrochloride of the amine, which first separated, rapidly dissolved and in a few minutes white needles began to separate. After 30 minutes the reaction mixture was cooled and filtered. The residue was washed with alcohol and then weighed. (2.5 g.) and had m.p. 266-267 with decomposition. Crystallisation from water furnished white glistening needles of unchanged meltingpoint. This hydrochloride was dissolved in hot water and the solution was made alkaline, thus precipitating l-(4-bromo-3,5-dichlorophenyl)-biguanide, m.p. 191 with effervescence. Thisbaseon recrystallisation from alcohol formed colourless prisms of the same m.p.

This biguanide (1.5 g.) was dissolved in normal aqueous ethanesulphonic acid ml.) and the solution was kept at 90 for 2 hours. 1sAmidino-3#(4-brorno-3,5 dichlorophenyl)urea ethanesulphonate separated from the hot liquid in white prismatic needles, which were collected and washed with water m.p. 245 with some decomposition.

EXAMPLE 26 3,4,5-Tribromoaniline (3.3 g.) was dissolved in hot alcohol (7.5 ml.) and to the solution were added dicyandiamide (2.52 g.) and 4N-hydrochloric acid (7.5 ml.). There was immediate separation of 3,4,5- tribromoaniline hydrochloride, but with wanning this redissolved, followed by separation of 1-(3,4,5-tribromophenyl)biguanide hydrochloride. After 30 minutes under reflux the reaction mixture was cooled and filtered. The product was washed with alcohol, leaving the hydrochloride as white matted needles (3.73 g.), m.p. 275.5 with decomposition. Recrystallisation from a large volume of water did not raise the melting point.

The base obtained'by treating a not aqueous solution of this salt with alkali had m.p. 193 with effervescence.

l-(3,4,5-tribromophenyl)biguanide (2.2 g.) was dissolved in normal aqueous ethanesulphonic acid (22 ml.) and the solution was kept at 90 for 2 hours. 1- Amidino-3-(3,4,5-tribromophenyl)urea ethanesulphonate crystallised in white prisms, which were fur ther purified by recrystallisation from methanol and then had m.p. 241 with decomposition. A hot aqueous solution of this salt, which was sparingly soluble in water, was made alkaline, yielding the base as white needles, which on recrystallisation from aqueous alcohol had m.p. 180 with effervescence, after partial melting at about 120 with loss of water of crystallisation followed by resolidification.

EXAMPLE 27 Tablets of l-amidino-3-(3,4,5-trichlorophenyl)urea were made from the following ingredients:

1. l-Amidino-3-(3,4,5-trichlorophenyl)urca 200 mg. 2. Starch B.P. 30 mg 3. Lactose B.P. mg 4. Gelatin B.P. 6 mg 5. Magnesium Stearate B.P. 4 mg Items 1, 2 and 3 were granulated with a solution of item 4 in 50 percent aqueous ethanol. Item 5 was added to the dried granules and the mixture compressed to form tablets.

EXAMPLE 28 In the manner described in Example 27 there were prepared tablets of the following compounds, each tablet containing 200 mg. of the active ingredient:

1-Amidino-3-(3,4,5-tribromophenyl)urea l-Amidino-3-(4-bromo-3,5-dichlorophenyl)urea.

EXAMPLE 29 An oral subpension of 1-amidino-3-(3,4,5- trichlorophenyl)urea was prepared from the following ingredients:

l-Amidino-3-( 3,4,5-

trichlorophenyl)urea mg. 2.0% w/v 2. Tragacanth B.P. 12 mg. 0.24% w/v 3. Acacia B.P. 15 mg. 0.3% My 4. Glycerin B.P. 300 mg. 6.0% w/v 5. Sorbitol B.P.C. 2.25 g. 45% w/v 6. Sucrose B.P. 2.0 g. 40% w/v 7. Purified Water B.P. to 5.0 ml. to 100.0%

A vehicle for the active ingredient was prepared containing items 2,3,4,5,6 and 7 by established pharmaceutical procedure. 15% of the vehicle was used to prepare an homogenous suspension of item 1 which was then diluted with the remainder of the prepared vehicle.

EXAMPLE 30 l-Amidino-3-(3,4,S- trichlorophenyl) 2. Water for lnjection B.P.

U rea or a pharmaceutically acceptable acid addition salt thereof wherein Y is nitrile, hydrogen, halogen or methyl and Y is halogen or nitrile provided that when Y is nitrile at the 3 position Y is halogen, and when 1* is nitrile Y is hydrogen, halogen or methyl at the 2- or 3- position; in association with a pharmaceutically acceptable carrier therefor.

2. A composition for use as an antimalarial which comprises an antimalarial effective amount of a compound of the formula or a pharmaceutically acceptable acid addition salt thereof wherein Y is halogen, hydrogen or methyl, Y is cyano, halogen, hydrogen or methyl, Y is cyano,

halogen, nitro or trifluoromethyl and Y is hydrogen;

provided that when Y is cyano, Y and Y are halogen, hydrogen or methyl and that at least one of Y and Y is hydrogen, and Y is hydrogen; and provided that when Y is halogen, Y is cyano, and both Y and Y are hydrogen; and further provided that one but not both of Y and Y is always cyano; in association with a pharmaceutically acceptable carrier therefor.

3. A composition according to claim 2 where halogen is chlorine, bromine or fluorine.

4. A composition for use as an antimalarial which comprises an antimalarial effective amount of a compound of the'formula or a pharmaceutically acceptable acid addition salt thereof where Y is methyl, halogen or hydrogen, Y is methyl, halogen, cyano or hydrogen, and Y is cyano or halogen; provided that when Y is cyano, Y and Y are halogen, hydrogen or methyl and that at least one of Y and Y is hydrogen; and provided that when Y is cyano, Y is halogen and Y is hydrogen; and further provided that one, but not both of Y and Y is always cyano; in association with a pharmaceutically acceptable carrier therefore.

5. A composition for use as an antimalarial which comprises an antimalarial effective amount of a compound of the formula or a pharmaceutically acceptable acid addition salt thereof where Y and Y are halogen or cyano provided that one of Y and Y is always cyano; in association with a pharmaceutically acceptable carrier therefore.

6. A composition for use as an antimalarial which comprises an antimalarial effective amount of lamidino-3'-(4-chloro-3-cyanophenyl)urea'or a pharmaceutically acceptable acid addition salt thereof, in association with a pharmaceutically acceptable carrier therefor.

7. A composition for use as an antimalarial which comprises an antimalarial effective amount of 1- amidino-3-(3-chloro-4-cyanophenyl)urea or a pharmaceutically acceptable acid addition salt thereof, in association with a pharmaceutically acceptable carrier therefor.

8. A composition for use as an antimalarial which comprises an antimalarial effective amount of lamidino-3-(3-chloro-4-cyanophenyl)urea or a pharmaceutically acceptable acid addition salt thereof in association with a pharmaceutically acceptable carrier 5 therefor in the form of a tablet.

9. A method for the treatment or prophylaxis of malaria in mammals comprising administering to the mammal in need thereof an effective antimalarial amount of a compound of the formula or a pharmaceutically acceptable acid addition salt thereof wherein Y is nitrile, hydrogen, halogen or methyl and Y is halogen or nitrile provided that when Y is nitrile at the 3 position Y is halogen, and when Y is nitrile, Y is hydrogen, halogen or methyl at the 2- or 3- position.

10. A method for the treatment or prophylaxis of malaria in mammals which comprises administering to a mammal in need thereof an effective antimalarial amount of a compound of the formula or a pharmaceutically acceptable acid addition salt thereof wherein Y is halogen, hydrogen or methyl, Y is cyano, halogen, hydrogen or methyl, Y is cyano, halogen, nitro or trifluoromethyl and Y is hydrogen; provided that when Y is cyano, Y and Y are halogen, hydrogen or methyl'and that at least one of Y and Y is hydrogen, and Y is hydrogen; and provided that when Y is halogen, Y is cyano, and both Y and Y are hydrogen; and further provided that one but not both of Y and Y is always cyano; in association with a pharmaceutically acceptable carrier therefor.

11. A method according to claim 10 wherein halogen is chlorine, bromine or fluorine.

12. A method for the treatment or prophylaxis of malaria in mammals which comprises administering to a mammal in need thereof an effective antimalarial amount of a compound of the formula 50 or a pharmaceutically acceptable acid addition salt thereof where Y is methyl, halogen or hydrogen, Y is methyl, halogen, cyano or hydrogen, and Y is cyano or halogen; provided that when Y is cyano, Y and Y are halogen, hydrogen or methyl and that at least one of Y and Y is hydrogen; and provided that when Y is cyano, Y is halogen and Y is hydrogen; and further provided that one, but not both of Y and Y is always cyano in association with a pharmaceutically acceptable carrier therefore.

13. A method for the treatment or prophylaxis of malaria in mammals which comprises administering to a mammal in need thereof an effective antimalarial amount of a compound of the formula or a pharmaceutically acceptable acid addition salt thereof where Y and Y are halogen or cyano provided that one of Y and Y is always cyano in association with a pharmaceutically acceptable carrier therefore. 14. A method for the treatment or prophylaxis of malaria in mammals which comprises administering to the mammal in need thereof an effective antimalarial amount of l-amidino-3-(3-chloro-4-cyanophenyl) urea or a pharmaceutically acceptable acid addition salt thereof.

@ 3 3? UNITED STATES PATENT OFFER v V CERTIFICATE OF CORRECTION Patent No. 3,761,597 Dated September 25 197% lnventofls) LESLIE PERCY WALLS It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Foreign App-iication Priority Data v July 7 1966 Great Btitaio .....30M79 Dec. 16, 1966 Great Britain .565H

- Feb. 3, 1967 Great Britain 0,5391 e 7 April 5, 1967 Great Britain Hutu-19028 1y Signed and seeled this 17th day of September 1 9 74.

(SEAL) Attest: V

MCCOY M. GIBSON JR'. v -C. MARSHALL DANN Attesting Officer r Commissioner of Patents 

2. A composition for use as an antimalarial which comprises an antimalarial effective amount of a compound of the formula
 3. A composition according to claim 2 where halogen is chlorine, bromine or fluorine.
 4. A composition for use as an antimalarial which comprises an antimalarial effective amount of a compound of the formula
 5. A composition for use as an antimalarial which comprises an antimalarial effective amount of a compound of the formula
 6. A composition for use as an antimalarial which comprises an antimalarial effective amount of 1-amidino-3-(4-chloro-3-cyanophenyl)urea or a pharmaceutically acceptable acid addition Salt thereof, in association with a pharmaceutically acceptable carrier therefor.
 7. A composition for use as an antimalarial which comprises an antimalarial effective amount of 1-amidino-3-(3-chloro-4-cyanophenyl)urea or a pharmaceutically acceptable acid addition salt thereof, in association with a pharmaceutically acceptable carrier therefor.
 8. A composition for use as an antimalarial which comprises an antimalarial effective amount of 1-amidino-3-(3-chloro-4-cyanophenyl)urea or a pharmaceutically acceptable acid addition salt thereof in association with a pharmaceutically acceptable carrier therefor in the form of a tablet.
 9. A method for the treatment or prophylaxis of malaria in mammals comprising administering to the mammal in need thereof an effective antimalarial amount of a compound of the formula
 10. A method for the treatment or prophylaxis of malaria in mammals which comprises administering to a mammal in need thereof an effective antimalarial amount of a compound of the formula
 11. A method according to claim 10 wherein halogen is chlorine, bromine or fluorine.
 12. A method for the treatment or prophylaxis of malaria in mammals which comprises administering to a mammal in need thereof an effective antimalarial amount of a compound of the formula
 13. A method for the treatment or prophylaxis of malaria in mammals which comprises administering to a mammal in need thereof an effective antimalarial amount of a compound of the formula
 14. A method for the treatment or prophylaxis of malaria in mammals which comprises administering to the mammal in need thereof an effective antimalarial amount of 1-amidino-3-(3-chloro-4-cyanophenyl) urea or a pharmaceutically acceptable acid addition salt thereof. 